1. ~ 90 2735 Delta IV 4040-121
2. Trajectory optimization was performed using Solar Electric Propulsion Trajectory Optimization Program (SEPTOP)18. SEPTOP is a two-body, Sun-centered, low-thrust trajectory optimization program for preliminary mission feasibility studies that provides relatively accurate performance estimates. The program determines a numerical solution to a two point boundary value problem that satisfies intermediate boundary constraints. In SEPTOP, the user estimates initial conditions, and then uses a shooting method to integrate the trajectory from an initial time to final time. SEPTOP computes an error at the final time and uses it to correct the estimate of the initial conditions. This process is repeated until the error becomes smaller than the prescribed tolerance. The required inputs are Time-of-flight, nominal Earth departure, array power at Earth departure, maximum power into Power Processing Unit (PPU), intermediate rendezvous body (in this case comet Tempel 1), and LV specifications. SEPTOP can model variable thrust and mass flow rate as a function of power into the PPU. The power generated from a solar array is modeled as a function of the spacecraft's distance from the Sun. Thruster and solar array models are thereforealsorequired asinputs.
3. SEPS assistedreturn to an Earthflybytoallowsamplereturnto Earth~1687days
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